The use of pressurized containers to dispense a wide variety of substances such as paint, cleaners etc. has been practiced for many years. Gaseous propellants such as the fluorocarbons, hydrocarbons, (condensed gases) or carbon dioxide (compressed gas) and the like have all been used for this purpose. Generally, in these systems, the material to be dispensed, if a solid such as in an antiperspirant, is suspended in a liquified propellant and is dispensed by the gaseous propellant. When the material to be dispensed is a liquid, it is either dispensed by the gaseous propellant as a single liquid phase having the liquified propellant dissolved therein or as a liquid per se with no liquified propellant. Usually, a valved eduction tube, open at its bottom, provides a passageway for the gaseous propellant to force the material to be dispensed upwardly therethrough and out of the container in which it is packaged. Systems of this type are known as two-phase systems, phase I being an upper layer of gaseous propellant and phase II being a liquid or a solid suspended in a liquid.
If, however, the material to be dispensed is of the nature of two immiscible liquids, for example, an aqueous solution and a liquified hydrocarbon propellant, difficulty is encountered. Such systems additionally contain a gaseous propellant and hence are known as three-phase systems. It has been found that conventional valve/diptube assemblies are incapable of dispensing properly the material to be dispensed uniformly from beginning to end when three-phase systems are involved. In a three-phase system, phase I is a gaseous propellent and phases II and III are two immiscible liquids, one of which may be a liquified propellant. An example of three-phase system is an aqueous solution of the material to be dispensed, phase I, a liquified hydrocarbon propellant, phase II, and gaseous hydrocarbon propellant, phase II.
In the dispensing of three-phase systems, conventionally, an aerosol valve at the top of a container is fitted with an eduction tube (or diptube) extending to a point near the inside bottom of the container and into the material to be dispensed. The material to be dispensed flows upwardly through the eduction tube under the influence of the internal can pressure in the valve housing and is dispensed through the valve button. A vapor tap, which usually opens into the body of the valve to mix gaseous propellant with the material stream, may also be included in the device.
Technology is available to formulate aerosol products, including such items as hair sprays, as solutions in water or in water-alcohol solutions, in which hydrocarbon propellants are insoluble. The problem with the use of such products is that because they are three-phase systems, their delivery by aerosol dispensing techniques is inadequate. One technique for handling such systems is described in U.S. Pat. No. 3,260,421.
If a dispensing technique which is more effective than those existing commercially at the present time could be devised, it would satisfy a long-felt need.